As described in co-pending U.S. application Ser. No. 799,862 filed May 23, 1977 entitled "Heat Stabilizer Composition for Halogenated Resins", certain alkaline earth metal mercaptides are particularly useful as synergists in conjunction with certain sulfur containing organotin or antimony compounds.
In the above cited patent application, the alkaline earth metal mercaptides are perpared in accordance with the following reactions; wherein M is the alkaline earth metal: EQU M + 2R'OH.fwdarw.M(OR').sub.2 + H.sub.2 (I) EQU m(or').sub.2 + 2hsr.fwdarw.m(sr).sub.2 + 2r'oh (ii)
the economics of carrying out such reactions commercially is less than ideal, as metals, M, are expensive. Other known methods by which certain metal alkoxides may be conveniently prepared are summarized by D. C. Bradley in "Progress in Inorganic Chemistry", Vol. 2 (edited by F. A. Cotton, Interscience Publishers, Inc., New York, N.Y., 1960, pp. 303ff). However, the only method cited by Bradley for preparing the alkaline earth metal alkoxides involves starting with the metal which is commercially uneconomical.
The oxides and hydroxides (hydrated or anhydrous) of the alkaline earth metals represent a much lower cost source for the metal M than the free metal itself.
The process of this invention provides a process for preparing the desired mercaptide starting with the corresponding metallic oxide or hydroxide; a relatively low-cost alkoxide of magnesium, aluminum or calcium; and an inexpensive alcohol. The other starting material required is a mercaptan of the corresponding desired metal mercaptide.